The control of complex machines and data handling systems frequently requires the generation of a large number of accurately timed signals to initiate the performance of various functions. In the past, the particular timings have been obtained in various ways. For example, counters may be set to some value and then decremented to zero by the application of pulses from a continuously running clock. Another technique is to provide single shot multivibrators set to various time durations thereby establishing an output signal at a certain interval after the occurrence of an initiating event. Either of these techniques perform accurately and reliably, but become expensive when large numbers of independent or unrelated timing signals are needed among diverse functions.
The provision of a counter or single shot and its required gates for each function to be controlled becomes prohibitive as to cost when dozens of timing signals are required. In addition, adjustment or change may be required after installation of the circuits as changes in function or circuit design occur. Many of the counters or single shots can be adjusted as to settable count or pulse duration but such changes are difficult and time consuming to accomplish, particularly when there are numerous changes to be made.
A further disadvantage has been noted in the data processing field in which the central processor control is required in many instances to provide counter settings or single shot initiation pulses. This, at times, conflicts with processing being carried on by the control unit and results in delays and repetition of certain program steps.
It is, accordingly, a primary object of this invention to provide apparatus in which timing signals for various functions can be accurately and reliably generated without the necessity of duplicating many of the control circuits heretofore required.
A further object of this invention is to provide apparatus for providing timing signals over a wide range of time intervals which eliminates the necessity of multiple clock frequencies heretofore required.
A still further object of this invention is to provide apparatus for producing timing signals in which several counts from the apparatus can be running concurrently.
Yet another object of this invention is to provide apparatus for producing timing signals which can be readily changed by merely addressing a memory unit.
A still further object of this invention is to provide apparatus for producing timing signals which is simple and relatively inexpensive, assembled from commonly used circuit modules and chips and lends itself to integrated circuit production.
Another important object of this invention is to provide apparatus for producing timing signals which is capable of relieving the central processing unit of dedicated monitoring control heretofore required in many instances.